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Optical Design & Engineering

Irresistible Innovation

Inspired by A.E. Conrady's optical design at a young age, David Shafer's work in and passion for optics has earned him the 2005 SPIE A.E. Conrady Award.

From oemagazine August 2005
31 August 2005, SPIE Newsroom. DOI: 10.1117/2.5200508.0011

While other boys were out riding bicycles and playing baseball, 13-year-old David Shafer was building a 6-inch aperture reflecting telescope from an Edmund Scientific kit. The clear, open skies surrounding the rural poultry farm near Syracuse, NY, where he grew up were an irresistibly perfect playground for the searching eyes of an amateur astronomer.

"There was no light pollution and our nearest neighbor was one mile away," Shafer recalls. "The optics of telescopes fascinated me. When I was 15 years old, I bought A.E. Conrady's two volumes on optical design at the Cornell University bookstore," he says. "Now I realize that visual optics, for me - a shy farm boy - represented a way to get very close to objects while still keeping my distance from them. Later I went to college at the University of Rochester [Rochester, NY] as one of five freshman optics majors at the Institute of Optics."

From these enterprising beginnings, a passion for optical design was born. Once the young man who purchased Conrady's books to pursue his budding interest in optical design, Shafer is now the 2005 recipient of the A.E. Conrady Award for his own vast work and development in the field. This award is given annually in recognition of exceptional contributions in design, construction, and testing of optical systems and instrumentation.

"Receiving the award is significant to me as a validation, I hope, of my emphasis on a particular kind of approach to optical design," Shafer says. "When I [first] bought Conrady's books, I read about how early designers - pre-computer - tried to squeeze every possible bit of information out of as few traced rays as possible, because of the odious amount of work hand calculations required. Understanding the designs and aberration theory was a very valuable way, back then, to avoid needless calculations. Now, 47 years later, I am saying that the best tool for the future is not a faster computer but rather that same search for human understanding of what is going on inside a design. A.E. Conrady would, I think, be pleased with this."

Shafer has been a full-time lens designer for the past 39 years. He began his career at Itek Corp. in Lexington, MA, where he designed aerial reconnaissance lenses and submarine detection optics. After five years at Itek, he went to Honeywell Electro-Optics (also in Lexington) and designed forward-looking infrared systems and military space optics. He moved on five years later to join the Perkin-Elmer Corp. in Wilton, CT, and designed more space optics and lithographic optics.

Shafer at work for his own optical design and consulting company, David Shafer Optical Design, in Fairfield, CT.

In 1980, Shafer started his own optical design and consulting company based in Fairfield, CT. His main focus has been the field of optical lithography. He has designed refractive lithographic systems for near- and deep-UV wavelengths, catadioptric systems for deep UV, reflective systems for extreme UV, and many deep-UV systems for wafer and reticle inspection.

"I hope that my main contribution to the field will not be my designs as much as it will be this emphasis I always place on how optical design can be a very expressive, personal experience, and how pure thought can bring something new into existence," Shafer says. "That makes it a very exciting profession. Computers are just tools to help us and cannot think and create for us. A few years ago, I invented a new perfect optical system. Unlike the three previously known perfect ones - a flat mirror, Maxwell's fish eye, and the Luneberg lens - this new perfect optical system forms a flat real image of a flat object. This new design was thought of without any computations at all, and it is extremely simple and aesthetically pleasing. No computer was involved."

Shafer holds about 70 patents, most in the field of lithography, and has presented more than 100 technical papers at SPIE and Optical Society of America (OSA) events. He has taught annual seminars in optical design for Sinclair Optics, SPIE short courses, a graduate course in geometrical optics and lens design at the University of Connecticut (Storrs, CT), and a lens design summer course at the Institute of Optics at the University of Rochester. Shafer is also a frequent referee of technical papers for OSA and SPIE journals, and is an OSA fellow.

"Education in optical design is very important to me. Many years of experience by seasoned designers have resulted in very valuable 'tricks' and design techniques that are rarely published," Shafer says. "Compared to other disciplines like mechanical or electrical design, there has been very little written about optical design, and almost none of that is about the actual process of optical design. Yet there are many very useful design techniques that can easily be taught in a short course or seminar. We old-timers who have learned a lot over the years can do a great service to others by sharing this experience through publications and short courses."

Although Shafer maintains his view that critical thinking is essential to the development of optical design, he continues to look for ways to combine his philosophical approach with modern technology and techniques.

"So far, the use of computers in design has almost entirely been for optimization and analysis. There has not been much attempt to use computers to help us understand these optical designs, and understanding is the best route to better designs," he says. "I think the biggest challenge for the future is to find a way for computers to help us in that way. Possibly computers could look for correlations between performance and various internal behaviors of rays inside the designs."